This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Measles virus (MV) is a natural human pathogen, but several species of Asian macaque and some other nonhuman primates are susceptible. The pathogenesis of measles is modeled very closely in rhesus and cynomolgus macaques. MV infection and disease, with significant mortality, can be widespread in primate colonies. Several primate centers, including the CNPRC, have used regular, annual measles vaccination to protect susceptible species from measles introduced by humans. This policy has been effective for many years;but currently, the measles or canine distemper vaccines that have been used successfully have been taken off the market. There has been no measles vaccination of primates at the CNPRC for the last 3 years. We have tested a molecularly cloned measles vaccine strain, derived from a vial of the Moraten strain measles vaccine, which we designate MVvac2. This virus infects rhesus monkeys with an attenuated pathogenesis, and the monkeys are protected from pathogenic MV challenge. This vaccine virus can be grown in Vero cells to titers of 105 - 106 tissue culture infectious doses per ml, thus it would be a practical vaccine for primate colony management. Vaccine stocks could be produced in large volume ( 100 doses) and cryopreserevd in aliquots that would be thawed immediately before use.